1. Field of the Invention
The present invention generally relates to a method and a device for continuous adaptation of coding parameters to a variable user-data rate, particularly within an ATSC-M/H datastream.
2. Related Art
U.S. Patent Application Publication 2007/0223612, which is hereby incorporated herein in its entirety by reference, describes a datastream with digital TV data configured according to the Advanced Television Systems Committee (ATSC) standard. Digital TV data for mobile receivers can be integrated and transmitted in the same datastream. Advanced Television Systems Committee Mobile/Handheld (ATSC-M/H) data are inserted as data blocks into ATSC-M/H timeslots provided for this purpose by the packet multiplexer of the TV transmitter. An ATSC-M/H timeslot contains either 156 ATSC-M/H transport stream data packets for mobile receivers or 118 ATSC-M/H transport stream data packets for mobile receivers and 38 ATSC-M/H transport stream data packets for stationary receivers.
The ATSC-M/H data packets from several mobile services are combined in an ATSC-M/H ensemble. The data of an ATSC-M/H ensemble are transmitted within an ATSC-M/H data frame in an ATSC-M/H parade. The data in an ATSC-M/H parade are encoded by a Reed-Solomon coder and stored encoded in a Reed-Solomon data frame. The data of an ATSC-M/H parade and accordingly of a Reed-Solomon data frame are distributed within one ATSC-M/H data frame by an interleaver. In each of the five ATSC-M/H data sub-frames associated with each ATSC-M/H data frame, a total of 16 ATSC-M/H timeslots are disposed. The data of one ATSC-M/H parade are stored respectively in an identical number of ATSC-M/H timeslots. Altogether, up to 16 ATSC-M/H parades can be distributed in an ATSC-M/H data frame. For each ATSC-M/H ensemble, up to 8 ATSC-M/H timeslots can be used in one ATSC-M/H data sub-frame. An example for the assignment of several ATSC-M/H parades to the individual ATSC-M/H timeslots of an ATSC-M/H data sub-frame is shown in FIG. 1.
The encoding of the ATSC-M/H data is typically implemented by a concatenated coding. The external coding of the individual ATSC-M/H parade is implemented with a Reed-Solomon coder, which adds to the user-data of the respective ATSC-M/H ensemble. Specifically, the Reed-Solomon coder adds a given number of parity symbols in every ATSC-M/H timeslot occupied by an ATSC-M/H parade and a given number of check-sum bits by a cyclical redundancy check (CRC) over the user-data and the parity symbols of the respective ATSC-M/H parade. An ATSC-M/H parade encoded by Reed-Solomon coding is stored in a Reed-Solomon data frame as shown in FIG. 2.
A Reed-Solomon data frame generated in this manner is composed of several segments of different sizes, which are assigned to several regions according to FIG. 3. Each region is encoded in a convolutional coder following the Reed-Solomon coder, which, together with the trellis coder of the 8-VSB modulator in the ATSC-M/H system, forms a serial concatenated convolutional code (SCCC).
FIG. 4A shows the number of user-data bytes capable of being transmitted in a Reed-Solomon data frame for various combinations of coding rates in the individual regions of an original Reed-Solomon frame. FIG. 4B shows the number of user-data bytes capable of being transmitted per ATSC-M/H timeslot for various combinations of coding rates in the individual regions of an original Reed-Solomon data frame and for various numbers (NoG) of ATSC-M/H timeslots per ATSC-M/H ensemble within an ATSC-M/H data sub-frame.
By varying the coding rate
  (            e      .      g      .                          ⁢      C        =                            1          2                ⁢                                  ⁢        and        ⁢                                  ⁢        C            =              1        4              )of the convolutional coder in every one of the 4 different regions of an ATSC-M/H parade, and by varying the number of parity symbols used (e.g. P=24, 36 and 48) in the case of the Reed-Solomon coder, a total of 48 different stages of error control for an ATSC-M/H parade is obtained.
Accordingly, the user-data rate of an ATSC-M/H ensemble or an ATSC-M/H parade in each ATSC-M/H data frame is dependent upon the error control configuration of the Reed-Solomon coder in the respective ATSC-M/H data frame, the error control configuration of the convolutional coder in the respective ATSC-M/H data frame and the number of ATSC-M/H timeslots provided for the ATSC-M/H ensemble in each of the five ATSC-M/H data sub-frames of the respective ATSC-M/H data frame.
For the transmission of the data from ATSC-M/H ensembles or ATSC-M/H parades, zero-data packets are reserved in the associated ATSC-M/H timeslots of the respective ATSC-M/H data frames within the ATSC-M/H transport datastream. If the transmission capacities of the individual mobile services are temporarily not used, these cannot be provided again to the ATSC data for stationary receivers and remain disadvantageously un-exploited.
The object of the invention is therefore to provide a method and a device in order to exploit in a beneficial manner temporarily unused transmission capacities of individual mobile services in a transport datastream.